The present invention relates to an image forming method and an image forming apparatus which performs image formation, such as a copying machine and a printer, especially, relates to an image forming apparatus and an image forming method which sets up a margin region.
In various kinds of image forming apparatus, such as a copying machine and a printer, a margin region on which an image is not formed is generally provided to an edge of a transfer sheet for prevention of dirt produced by toner scattering within an apparatus and for prevention of deficit of an image, etc.
When an image is formed near to the edge of a transfer sheet as nearer as possible, toner which should be transferred to the edge of a transfer sheet scatters to conveyance members such as a guide plate and a roller not to the edge of a transfer sheet being a true transfer position due to causes such as a run gap of a transfer sheet and an error of transfer paper size.
And the toner transferred to the conveying member will adhere near the edge of the following transfer sheet, and will spread as dirt of a transfer sheet, and dirt of each part of the inside of an apparatus. For this reason, in general image forming apparatus, a fixed margin defined beforehand was provided for a transfer sheet at the time of image formation such that scattering of toner to a conveying member and dirt resulting from this toner scattering might not take place.
On the other hand, as a user, there is a case desire to form an image in the whole transfer sheet without forming a margin. Then, when not forming a margin, a special mode different from a usual image formation mode and to change a carrying speed to a low speed was operated such that the run gap mentioned above might not take place.
Incidentally, various kinds of proposals were made by the following patent documents as techniques of this kind of margin preparation.
According to the technique by the Japanese Patent Unexamined Publication No. 5-216333, the imaging region of a transfer sheet is restricted by controlling transfer current, whereby toner scattering is suppressed and dirt of the edge portion of a transfer sheet is reduced. However, the problem which this technique can cope with only the leading end and the trailing end of a transfer sheet transportation direction (sub scanning direction) is left behind.
According to the technique by the Japanese Patent Unexamined Publication No. 2001-18443, this technique relates a technique to correctly control the timings of the leading and trailing ends of a laser beam by masking signals, and further relates to a technique to control each masking signal in the case of using a plurality of beams. Therefore, a problem which the technique merely control the start position of a main scanning direction and a terminal position of the main scanning direction.
According to the technique by the Japanese Patent Unexamined Publication No. 2003-266854, this technique is to select whether a margin region is formed or not. In the case that a margin region is formed, this technique changes an image size. Therefore, this publication does not disclose the technique regarding a proper margin not causing dirt.
According to the technique by the Japanese Patent Unexamined Publication No. 2002-333743, by controlling a developing section and a transferring section so as to limit an image density, this technique refrains toner scattering and reduces dirt on an end portion of a transfer sheet. However, this technique merely regulates image density by changing a developing bias. Therefore, the problem which this technique can cope with only the leading end and the trailing end of a transfer sheet transportation direction (sub scanning direction) is left behind.
According to the technique by the Japanese Patent Unexamined Publication No. 2003-127341, this technique relates to an inkjet and is to restrict ink jetting on an end portion of a transfer sheet. Therefore, the problem which this technique can't be applied to an electro-photographic type image forming apparatus employing toner is left behind.